Intelligentes Magnetventil für Wasserstofftankstellen
4. März 2019
Die Nova Werke AG hat ein intelligentes Magnetventil für Wasserstofftankstellen entwickelt. Der Hauptventilkörper ist optimal auf den SLM-Prozess abgestimmt und integriert verschiedene Sensoren - weshalb dieser Showcase für den Swiss AM Guide 2019 ausgewählt wurde.
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In order to promote the adoption of environmental friendly energy resources for mobility, fuel cells play an important role. Briefly explained, hydrogen gas is used to chemically react to water while generating an electric current, which can be used to power a vehicle. Compared to conventional electric cars with batteries, fuel cell powered vehicles tend to have a greater range and can be refueled substantially faster. If the hydrogen gas is generated with green energy resources (e.g. wind or water), the environmental footprint is much better compared to lithium based batteries. Still, fuel cell cars have not made their breakthrough yet, mostly due to a sparse hydrogen refueling network. Nova Werke AG, a Swiss technology company based in Effretikon, has developed a solenoid valve for hydrogen gas stations. The valve body is specifically designed for the Selective Laser Melting process. The joint development project with Inspire shall be discussed within this showcase.
Description of the Showcase
As depicted in Figure 1, the presented part is a solenoid actuated valve, which controls the flow of hydrogen gas in a filling station. Since pressures can reach up to 1000 bar, the design is based on a pilot valve to reduce the needed actuation force. Special focus was set on minimizing the size of the valve. As a result, the four closely positioned outlets are connected by complexly shaped, high-pressure gas-carrying pipe structures.
The overall design was consistently optimized in order to reduce post processing efforts to a minimum. Finishing encompasses mechanical machining of all valve connectors to satisfy requirements regarding accuracy or surface quality. For example, all in- and outlets were arranged vertically and at the same height to make mechanical finishing as easy as possible. Furthermore, drop-shaped pipe sections were applied to avoid support structures whenever possible.
Further innovativeness of the part lies in its integration of sensors into the SLM structure. The goal was to enable intelligent features, as for example report of valve status. As a result, two temperature and one Hall sensor are introduced into the assembly. In order to integrate the sensors, the build job is interrupted and the sensors are positioned in pre-built cavities. Afterwards, the build process can be continued. The vertical positioning of all three sensors was arranged as such that only one built job interruption is required. Cable guiding was also integrated into the SLM part. For all this features two patent applications have been filed.
The joint development project between Nova and Inspire was conducted in an iterative manner. Starting with a design thinking driven workshop, user personas and first concepts of the valve were created. Afterwards, multiple iterations of the part were designed. Even late in the project, conceptual changes were allowed to improve the overall performance of the product. For instance, the part orientation was flipped up side down very late in the project in order to allow hybrid manufacturing on top of a conventionally manufactured plate. Even though the CAD model had to be substantially remodeled, the benefits were much bigger since the part volume was reduced by 40%. In order to precisely position the print job on the build plate, positioning guides were introduced as well.
Throughout the whole project, physical testing of the SLM prototypes was prioritized. SLM probes were frequently tested regarding aspects as long term durability or the effect of print job interruption on material strength. The project team spend one year to investigate static and dynamic properties, including gas-tightness, based on probes. Findings were reintroduced into the design of the solenoid valve.
To sum up, Nova’s SLM solenoid valve impressively shows how part design, functionality and processes have to be consistently aligned to each other. As seen in the example of the sensor integration or the shape of the gas-carrying pipes, the selection of a certain manufacturing and finishing process has an immediate impact on the valve’s design and functionality. Only by proper alignment, the full potential of Additive Manufacturing can be exploited. In the future, Nova is looking forward to optimize the part regarding cost reduction and quality assurance for a serial production.
Pulverbettverfahren Metall und Keramik (SLM, EBM, etc.)